Difference between revisions of "Dune stabilisation"
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| + | [[Dune]]s are a natural coastal feature on moderately exposed and exposed sandy coasts. [[Dune]]s are formed by sand from the beach, which is blown inland by the wind – see the article [[Dune development]]. | ||
==Background== | ==Background== | ||
| − | During storm surge events, | + | During [[Extreme storms|storm surge events]], [[dune]]s can be eroded but the eroded sand generally remains in the [[active coastal zone]]. This natural littoral sand belt therefore forms a flexible buffer zone that protects the hinterland from flooding and contributes to minimizing shoreline retreat. During storms and also under less severe conditions, sand will be transported inland, sometimes in connection with the formation of wind alleys in the dune row. After a storm, the damaged [[dune]] is gradually rebuilt by natural processes: the dune belt constitutes a resilient coast protection and sea defense system. The dune belt of a coast at equilibrium maintains its form and volume as well as a wide beach, while moving backwards when the shoreline retreats and forward when the shoreline advances. The [[erosion]] of [[dune]]s as a result of a severe storm surge is also referred to as [[dune erosion]]. The article [[Dune erosion]] gives a more detailed description of dune erosion processes and the article [[Shoreline retreat and recovery]] deals with after-storm recovery processes. |
| − | + | ==Dune vegetation== | |
| + | Barren dunes are susceptible to [[deflation]] by wind, with landward dune migration taking place. Vegetation plays an important role in stabilizing dunes. A variety of natural vegetation species can settle on the beach and the foredune and are adapted to retain drifting sand. An overview of sand binding plants that are adapted to saline, nutrient-poor and harsh hydro-sedimentary conditions can be found in the article [[Shore protection vegetation]]. Beach and foredune vegetation typically require regular sand burial for healthy growth, resulting in the formation of deep, layered root structures. Flume experiments and field observations show that such root systems, especially dense fine root structures, contribute more to erosion control than the above-ground biomass<ref>Figlus, J., Sigren, J.M., Feagin, R.A. and Armitage, A.R. 2022. The unique ability of fine roots to reduce Vegetated Coastal dune erosion during wave collision. Front. Built Environ. 8:904837</ref><ref name=A25>Ahrenbeck, L., Lojek, O., Schattmann, J., Mehrtens, B., Schweiger, C., Kosmalla, V., Schürenkamp, D. and Goseberg, N. 2025. Surrogate root system modeling—A hybrid dune reinforcement. Coastal Engineering 202, 104835</ref>. It therefore takes time before the potential of new planted vegetation to mitigate erosion is fully developed. | ||
| − | + | [[Dune]] stabilisation by vegetation is a sustainable protection measure, enhancing the natural protection ability of dune areas. It provides partial protection against wave and storm surge attack and at the same time it preserves the natural character of the coastal landscape. Dune stabilization requires a planned and coordinated effort. However, the natural protection provided by beach and dune vegetation will be impaired if the plants are damaged by grazing or if beach-users, etc. generate too much traffic. Some uses such as golf courses typically fail to allow a sand dune system to move naturally. On the other hand, sand blown into the hinterland can cause serious disruption to economic activities taking place there. Consequently, authorities normally tend to protect dunes by regulating their use. | |
| − | + | [[Image:Marram planting.jpg|thumb|right|300px|Fig. 1. Marram planting and the placing of spruce fascines in wind alleys (Danish Coastal Authority<ref>Danish Coastal Authority, 1998. "Menneske, Hav, Kyst og Sand". (in Danish), (Man, Sea Coast and Sand in English). Kystinspektoratet 1973-1998.</ref>).]] | |
| − | [[Image:Marram planting.jpg|thumb|Fig. 1. Marram planting and the placing of spruce fascines in wind alleys (Danish Coastal Authority<ref>Danish Coastal Authority, 1998. "Menneske, Hav, Kyst og Sand". (in Danish), (Man, Sea Coast and Sand in English). Kystinspektoratet 1973-1998.</ref>).]] | ||
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| − | Newly planted vegetation in particular can be strengthened by using fertiliser. | + | In some cases authorities have been eager to protect the [[dune]]s by planting [[marram grass]] and placing fences or fascines (placing of pine or spruce branches) in the wind alleys to trap the sand <ref name=N1>NSW 2001. Coastal Dune Management: A Manual of Coastal Dune Management and Rehabilitation Techniques. New South Wales, Department of Land and Water Conservation, Australia, http://www.environment.nsw.gov.au/resources/coasts/coastal-dune-mngt-manual.pdf </ref><ref>USACE 2008. Coastal Engineering Manual. Part V, Ch. 7. Coastal Engineering for Environmental Enhancement pp. V.7.17-V.7.21. https://www.publications.usace.army.mil/USACE-Publications/Engineer-Manuals/u43544q/636F617374616C20656E67696E656572696E67206D616E75616C/</ref>. |
| + | Larger wind alleys can also be filled artificially prior to planting. Newly planted vegetation in particular can be strengthened by using fertiliser. However, in some cases, planting marram grass has resulted in complete fixing of the dune position and an unnatural growth in height. If the flexibility of the natural dune is lost, this can even result in a gradual disappearance of the [[dune]] due to erosion, whereby the protection provided by the natural [[dune]] system, is lost. | ||
| − | + | If suitable sand-binding vegetation species for dune protection are not available, for example, due to climatic or sedimentary conditions, the use of artificial surrogates can be considered. Laboratory experiments have demonstrated the effectiveness of coconut mats inserted horizontally in the dune face to mimic the sand-binding function of natural root systems. However, since natural materials are susceptible to biodegradation, the sustainability of such measures is a concern<ref name=A25/>. | |
| − | == | + | ==Restoring natural dune dynamics== |
| − | + | Urgent interventions to restore or reinforce dunes can be necessary in some cases. In most cases, however, better results are achieved by restoring the conditions for natural dune development. Promoting natural dune development requires limiting negative interferences. Structures that obstruct sand supply to the beach by interrupting littoral drift should be removed, or otherwise compensated by [[Sand by-pass systems|sand bypassing]] systems or by sand [[Shore nourishment|nourishment]] of the beach or foreshore. Grazing in dune areas is prohibited in most countries, and authorities often limit public access. Such restrictions may also regulate the traffic in the dunes, e.g., ban on motor traffic, paved walking passages in areas near parking lots and fencing natural dune areas (especially fragile newly planted zones). Mechanical beach clearing can destroy vegetation and incipient foredunes; boardwalks, seawalls and beachside residential homes obstruct the beach-dune continuum. Urbanized hinter-dune areas restrict the environmental gradient and impede natural dune development. Natural variability is an important characteristic of natural dune development processes. This implies the exchange of sediment (with the dune, the beach and near the coast), nutrients and biota, as well as the natural cycles of accretion, erosion, growth and decay, so that greater diversity and complexity ultimately results in greater resilience of the foredune system<ref>Doyle, T.B. and Woodroffe, C.D. 2023. Modified foredune eco-morphology in southeast Australia. Ocean and Coastal Management 240, 106640</ref>. Topographical variability contributes to subtle but valuable variations in microclimate and habitat<ref name=N1/>. | |
| + | |||
| + | Restoration of the conditions for natural dune development may conflict with the interests of beach tourists and residents (e.g., obstructed sea view due to high dunes or vegetation). A long-term strategy for coordinated management of land within the coastal zone therefore requires public consultation and participation to adequately address the social, economic and cultural aspects involved. | ||
==Applicability== | ==Applicability== | ||
| − | Dune stabilisation is applicable on all coastal types where natural dunes occur. This is especially the case on moderately exposed to exposed coasts with perpendicular to very oblique wave (wind) attacks, | + | [[Dune]] stabilisation is applicable on all coastal types where natural dunes occur. This is especially the case on moderately exposed to exposed coasts with perpendicular to very oblique wave (wind) attacks. There is ample evidence for the effectiveness of sand fences to promote dune growth in periods of strong onshore winds, provided these are not accompanied by high water levels and waves. Several examples show that sand fences can also increase the stability of the dune belt during heavy storms<ref>Harris, M.E., Ellis, J.T. and Barrineau, P. 2020. Evaluating the geomorphic response from sand fences on dunes impacted by hurricanes. Ocean and Coastal Management 193: 105247</ref>. |
| + | |||
| + | ==Artificial hard dune core== | ||
| + | In some cases, dunes overlie old layers of highly erodible materials such as peat or clay. These layers can become exposed when the sandy dune front is eroded during severe long-lasting storms or storm clusters (rapid storm sequences). The washing away of these erodible layers can lead to dune collapse. Such inhomogeneous dunes can be strengthened by incorporating an artificial hard core. Dunes along the microtidal Baltic coast in Poland are internally reinforced with gabions and geotextile mattresses<ref>Rozynski, G. 2023. Coastal protection challenges after heavy storms on the Polish coast. Continental Shelf Research 266, 105080</ref>. These reinforcement materials account for only about 1% of the dune's volume. The eroded sand dune front is restored by means of sand nourishments, so that important ecosystem services are preserved, such as forest-dune-beach continuity and connectivity for coastal wildlife. | ||
| + | |||
| + | In the Netherlands, a hard artificial dune core has been applied in places where a single coastal dune row protects land below sea level. In one case (coastal village of Katwijk), the hard dune core was designed to also serve as a parking lot for beach tourists. | ||
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| + | |||
| + | Examples of artificial dunes serving as sea defence structures are discussed in the article [[Climate adaptation measures for the coastal zone]]. | ||
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| + | ==Related articles== | ||
| + | :[[Shore protection vegetation]] | ||
| + | :[[Dune development]] | ||
| + | :[[Dune erosion]] | ||
| + | :[[Shoreline management]] | ||
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==References== | ==References== | ||
<references/> | <references/> | ||
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| − | + | ==Further reading== | |
| − | + | Mangor, K., Drønen, N. K., Kaergaard, K.H. and Kristensen, N.E. 2017. Shoreline management guidelines. DHI https://www.dhigroup.com/marine-water/ebook-shoreline-management-guidelines. | |
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| − | == | + | {{2Authors |
| − | : | + | |AuthorID1=13331 |
| + | |AuthorFullName1=Mangor, Karsten | ||
| + | |AuthorName1=Karsten | ||
| + | |AuthorID2=120 | ||
| + | |AuthorFullName2=Job Dronkers | ||
| + | |AuthorName2=Dronkers J | ||
| + | }} | ||
| + | |||
| + | [[Category:Coastal protection]] | ||
| + | [[Category:Soft coastal interventions]] | ||
| + | [[Category:Beaches]] | ||
Latest revision as of 13:02, 30 November 2025
Dunes are a natural coastal feature on moderately exposed and exposed sandy coasts. Dunes are formed by sand from the beach, which is blown inland by the wind – see the article Dune development.
Contents
Background
During storm surge events, dunes can be eroded but the eroded sand generally remains in the active coastal zone. This natural littoral sand belt therefore forms a flexible buffer zone that protects the hinterland from flooding and contributes to minimizing shoreline retreat. During storms and also under less severe conditions, sand will be transported inland, sometimes in connection with the formation of wind alleys in the dune row. After a storm, the damaged dune is gradually rebuilt by natural processes: the dune belt constitutes a resilient coast protection and sea defense system. The dune belt of a coast at equilibrium maintains its form and volume as well as a wide beach, while moving backwards when the shoreline retreats and forward when the shoreline advances. The erosion of dunes as a result of a severe storm surge is also referred to as dune erosion. The article Dune erosion gives a more detailed description of dune erosion processes and the article Shoreline retreat and recovery deals with after-storm recovery processes.
Dune vegetation
Barren dunes are susceptible to deflation by wind, with landward dune migration taking place. Vegetation plays an important role in stabilizing dunes. A variety of natural vegetation species can settle on the beach and the foredune and are adapted to retain drifting sand. An overview of sand binding plants that are adapted to saline, nutrient-poor and harsh hydro-sedimentary conditions can be found in the article Shore protection vegetation. Beach and foredune vegetation typically require regular sand burial for healthy growth, resulting in the formation of deep, layered root structures. Flume experiments and field observations show that such root systems, especially dense fine root structures, contribute more to erosion control than the above-ground biomass[1][2]. It therefore takes time before the potential of new planted vegetation to mitigate erosion is fully developed.
Dune stabilisation by vegetation is a sustainable protection measure, enhancing the natural protection ability of dune areas. It provides partial protection against wave and storm surge attack and at the same time it preserves the natural character of the coastal landscape. Dune stabilization requires a planned and coordinated effort. However, the natural protection provided by beach and dune vegetation will be impaired if the plants are damaged by grazing or if beach-users, etc. generate too much traffic. Some uses such as golf courses typically fail to allow a sand dune system to move naturally. On the other hand, sand blown into the hinterland can cause serious disruption to economic activities taking place there. Consequently, authorities normally tend to protect dunes by regulating their use.
In some cases authorities have been eager to protect the dunes by planting marram grass and placing fences or fascines (placing of pine or spruce branches) in the wind alleys to trap the sand [4][5]. Larger wind alleys can also be filled artificially prior to planting. Newly planted vegetation in particular can be strengthened by using fertiliser. However, in some cases, planting marram grass has resulted in complete fixing of the dune position and an unnatural growth in height. If the flexibility of the natural dune is lost, this can even result in a gradual disappearance of the dune due to erosion, whereby the protection provided by the natural dune system, is lost.
If suitable sand-binding vegetation species for dune protection are not available, for example, due to climatic or sedimentary conditions, the use of artificial surrogates can be considered. Laboratory experiments have demonstrated the effectiveness of coconut mats inserted horizontally in the dune face to mimic the sand-binding function of natural root systems. However, since natural materials are susceptible to biodegradation, the sustainability of such measures is a concern[2].
Restoring natural dune dynamics
Urgent interventions to restore or reinforce dunes can be necessary in some cases. In most cases, however, better results are achieved by restoring the conditions for natural dune development. Promoting natural dune development requires limiting negative interferences. Structures that obstruct sand supply to the beach by interrupting littoral drift should be removed, or otherwise compensated by sand bypassing systems or by sand nourishment of the beach or foreshore. Grazing in dune areas is prohibited in most countries, and authorities often limit public access. Such restrictions may also regulate the traffic in the dunes, e.g., ban on motor traffic, paved walking passages in areas near parking lots and fencing natural dune areas (especially fragile newly planted zones). Mechanical beach clearing can destroy vegetation and incipient foredunes; boardwalks, seawalls and beachside residential homes obstruct the beach-dune continuum. Urbanized hinter-dune areas restrict the environmental gradient and impede natural dune development. Natural variability is an important characteristic of natural dune development processes. This implies the exchange of sediment (with the dune, the beach and near the coast), nutrients and biota, as well as the natural cycles of accretion, erosion, growth and decay, so that greater diversity and complexity ultimately results in greater resilience of the foredune system[6]. Topographical variability contributes to subtle but valuable variations in microclimate and habitat[4].
Restoration of the conditions for natural dune development may conflict with the interests of beach tourists and residents (e.g., obstructed sea view due to high dunes or vegetation). A long-term strategy for coordinated management of land within the coastal zone therefore requires public consultation and participation to adequately address the social, economic and cultural aspects involved.
Applicability
Dune stabilisation is applicable on all coastal types where natural dunes occur. This is especially the case on moderately exposed to exposed coasts with perpendicular to very oblique wave (wind) attacks. There is ample evidence for the effectiveness of sand fences to promote dune growth in periods of strong onshore winds, provided these are not accompanied by high water levels and waves. Several examples show that sand fences can also increase the stability of the dune belt during heavy storms[7].
Artificial hard dune core
In some cases, dunes overlie old layers of highly erodible materials such as peat or clay. These layers can become exposed when the sandy dune front is eroded during severe long-lasting storms or storm clusters (rapid storm sequences). The washing away of these erodible layers can lead to dune collapse. Such inhomogeneous dunes can be strengthened by incorporating an artificial hard core. Dunes along the microtidal Baltic coast in Poland are internally reinforced with gabions and geotextile mattresses[8]. These reinforcement materials account for only about 1% of the dune's volume. The eroded sand dune front is restored by means of sand nourishments, so that important ecosystem services are preserved, such as forest-dune-beach continuity and connectivity for coastal wildlife.
In the Netherlands, a hard artificial dune core has been applied in places where a single coastal dune row protects land below sea level. In one case (coastal village of Katwijk), the hard dune core was designed to also serve as a parking lot for beach tourists.
Examples of artificial dunes serving as sea defence structures are discussed in the article Climate adaptation measures for the coastal zone.
Related articles
References
- ↑ Figlus, J., Sigren, J.M., Feagin, R.A. and Armitage, A.R. 2022. The unique ability of fine roots to reduce Vegetated Coastal dune erosion during wave collision. Front. Built Environ. 8:904837
- ↑ 2.0 2.1 Ahrenbeck, L., Lojek, O., Schattmann, J., Mehrtens, B., Schweiger, C., Kosmalla, V., Schürenkamp, D. and Goseberg, N. 2025. Surrogate root system modeling—A hybrid dune reinforcement. Coastal Engineering 202, 104835
- ↑ Danish Coastal Authority, 1998. "Menneske, Hav, Kyst og Sand". (in Danish), (Man, Sea Coast and Sand in English). Kystinspektoratet 1973-1998.
- ↑ 4.0 4.1 NSW 2001. Coastal Dune Management: A Manual of Coastal Dune Management and Rehabilitation Techniques. New South Wales, Department of Land and Water Conservation, Australia, http://www.environment.nsw.gov.au/resources/coasts/coastal-dune-mngt-manual.pdf
- ↑ USACE 2008. Coastal Engineering Manual. Part V, Ch. 7. Coastal Engineering for Environmental Enhancement pp. V.7.17-V.7.21. https://www.publications.usace.army.mil/USACE-Publications/Engineer-Manuals/u43544q/636F617374616C20656E67696E656572696E67206D616E75616C/
- ↑ Doyle, T.B. and Woodroffe, C.D. 2023. Modified foredune eco-morphology in southeast Australia. Ocean and Coastal Management 240, 106640
- ↑ Harris, M.E., Ellis, J.T. and Barrineau, P. 2020. Evaluating the geomorphic response from sand fences on dunes impacted by hurricanes. Ocean and Coastal Management 193: 105247
- ↑ Rozynski, G. 2023. Coastal protection challenges after heavy storms on the Polish coast. Continental Shelf Research 266, 105080
Further reading
Mangor, K., Drønen, N. K., Kaergaard, K.H. and Kristensen, N.E. 2017. Shoreline management guidelines. DHI https://www.dhigroup.com/marine-water/ebook-shoreline-management-guidelines.
Please note that others may also have edited the contents of this article.
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